1. Field of the Invention
The present invention relates to an apparatus for testing an integrated circuit (hereinafter referred to as xe2x80x9cICxe2x80x9d), and more particularly to an apparatus for testing an IC which comprises both digital and analog circuit components.
2. Description of the Related Art
One conventional IC testing apparatus is shown in FIG. 7 of the accompanying drawings. As shown in FIG. 7, the conventional IC testing apparatus has a power supply 1, a controller 2, a time-based synchronizing system 3 for synchronizing various measuring components with a given timing signal, and a device interface 4 for connecting the measuring components to an IC device under test. The conventional IC testing apparatus also has, as its measuring components, a digital I/O device (often a plurality of digital I/O devices) 5 for exchanging digital signals with a digital signal terminal of the IC device under test to determine whether the IC device under test is acceptable or not, an audio-band AWG (Arbitrary Waveform Generator) 6 and a video-band AWG 7 for applying known signals to an analog signal input terminal of the IC device under test, and an audio-band digitizer 8 and a video-band digitizer 9 for detecting a signal from an analog signal output terminal of the device under test to determine whether the IC device under test is acceptable or not. The conventional IC testing apparatus may have a plurality of AWGs and a plurality of digitizers having different bands and different resolutions depending on the signal frequency that is handled and the required level of accuracy.
For testing an IC device, the conventional IC testing apparatus applies a predetermined signal to the IC device under test, and compares an output signal from the IC device under test with an expected value. For testing an IC which comprises both digital and analog circuit components, it is necessary to perform a digital output test using a digital comparator and an analog output test using an analog comparator.
Specifically, a digital test signal generated by a digital signal generator is applied to the IC under test, and an analog signal outputted from the IC under test is converted by an analog-to-digital converter into numerical data, which is stored in a capture memory. Thereafter, a processor processes the numerical data stored in the capture memory to calculate parameters necessary to evaluate analog output characteristics of the IC under test, and determines whether the IC under test is acceptable or not using the parameters. A digital signal outputted from the IC under test is compared with a value expected from an acceptable IC by a digital signal evaluation apparatus to determine whether the IC under test is acceptable or not.
According to the above conventional process, different testing units are used to test digital and analog output signals from an IC which comprises both digital and analog circuit components. Therefore, it is necessary to test such an IC with two testers, i.e., a digital IC tester and an analog IC tester, or a single large-scale IC tester comprising digital and analog test circuits.
Conventionally, the test system needs to have optimum test devices for handling respective attributes (e.g., digital and analog natures, frequency bands, resolutions, etc.) of a signal applied to or outputted from a device under test. Furthermore, testing a variety of devices requires a number of test devices having different performances to be available on hand.
In each test, the test device must be connected to corresponding terminals of the device under test. Such connections may need to be changed depending on the item to be measured. Changing connections makes the test time-consuming because it causes mechanical connectors such as relays to be turned on and off. Since terminal layouts of devices under test generally differ from device to device, it is necessary to prepare connecting jigs dedicated for the respective devices under test.
According to the recent trends of multifunctional ICs, there is a growing number of ICs in which a large-scale digital circuit and a simple analog circuit are integrated. Preparing a large-scale analog testing circuit for use with ICs comprising digital and analog circuit components makes the cost of testing ICs high.
It is an object of the present invention to provide an apparatus of simple structure which has functions and performances that have been carried out by a plurality of conventional testing apparatuses.
According to the present invention, there is provided an apparatus for testing an integrated circuit in analog and digital components of a device under test by monitoring an analog signal and a digital signal outputted from the integrated circuit, comprising a comparator, a memory for receiving an output signal from the comparator, a driver for receiving an output signal from the memory, an adder or subtractor which may accept an analog signal outputted from the integrated circuit and a signal outputted from the memory, an integrator which accepts an analog signal outputted from the adder or subtractor, a first switch for selectively transmitting an analog signal outputted from the integrator and a digital signal outputted from the integrated circuit to the comparator, and a second switch for selectively transmitting a signal outputted from the memory and a signal outputted from the comparator to the driver, wherein at least one of the switches is operated depending on whether a signal to be tested from the integrated circuit of the device under test is an analog signal or a digital signal. The apparatus may further comprise a third switch and a digital filter which are connected between the comparator and the memory, for transmitting the signal outputted from the comparator selectively via the digital filter to the memory.
The present invention also provides an apparatus for testing an integrated circuit in analog and digital components of a device under test by monitoring an analog signal and a digital signal outputted from the integrated circuit, comprising a comparator, a memory for receiving an output signal from the comparator, a driver for receiving an output signal from the memory, an adder or subtractor which may accept an analog signal outputted from the integrated circuit and a signal outputted from the driver, an integrator which accepts an analog signal outputted from the adder or subtractor, a first switch for selectively transmitting an analog signal outputted from the integrator and a digital signal outputted from the integrated circuit to the comparator, and a second switch for selectively transmitting a signal outputted from the memory and a signal outputted from the comparator to the driver, wherein at least one of the switches is operated depending on whether a signal to be tested from the integrated circuit of the device under test is an analog signal or a digital signal. This apparatus may also further comprise a third switch and a digital filter which are connected between the comparator and the memory, for transmitting the signal outputted from the comparator selectively via the digital filter to the memory. The apparatus may further comprise a delay circuit connected between the comparator and the adder or the subtractor. The apparatus may further comprise a delay circuit connected between the comparator and the second switch. In the apparatus, the driver may be disposed in a feedback loop extending from the comparator to the adder or the subtractor.
The testing apparatus according to the present invention can test a plurality of items without changing connections between itself and the integrated circuit under test. If integrated circuits to be tested have terminals at identical positions, then the testing apparatus can test different integrated circuits without changing connections. The testing apparatus can thus test integrated circuits at a reduced test cost.
While it has generally been practiced to input a digital signal to and output a digital signal from one apparatus, the present invention makes it possible for one testing apparatus to input and output a digital signal and also to input and output an analog signal. The digital and analog signal inputting and outputting capability unifies the components enclosed by the dotted line in FIG. 7, i.e., the digital I/O 5, the audio-band AWG 6, the video-band AWG 7, the audio-band digitizer 8, and the video-band digitizer 9.